Los Angeles — It’s a long, laborious, and ultimately costly gesture, economists warn, but more US cities are joining the pile-on of boycotts designed to sock Arizona for its tough new immigration policy.

The Arizona immigration law, requiring police to determine a person’s immigration status if there is a reasonable suspicion about the suspect's legal status, was signed April 24 to go into effect within 90 days. Arizona lawmakers last week changed the language of the bill to require scrutiny only of people who police already have stopped, detained or arrested for other reasons.

Do such moves produce tangible pressure, or are they just symbolic, toothless gestures? And what are the precedents for a city suing its own state?

The answer to the first question is yes, the pressure is real, say experts. The answer to the second is less clear.

“Plenty of blue state dollars are spent each year on conventions in Phoenix and trips to the Grand Canyon, so as boycott efforts brew in localities from California to New York, the potential for economic damage is real,” says Matthew Kerbel, a political science professor at Villanova University. When Arizona was boycotted in 1993 for refusing to observer Martin Luther King day, Mr Kerbel says, it lost 130 conventions and the Super Bowl – as much as $350 million by some estimates. Now the potential impact has grown.

“When you add the social networking capability of the Internet to the mix, you have the potential for a fairly robust and widespread boycott,” says Kerbel.

Boston officials have reportedly already identified one contract – a $1.1 million agreement between the Boston Centers for Youth & Families and an Arizona software firm – and say there may be others. The Boston resolution calls for the city to review its investments in Arizona or state municipal bonds, and to review travel by city employees to Arizona for conferences and other official business. Boycotts, others say, have already had a desired effect: Some corporations and organizations have already canceled their plans in Arizona cities such as Phoenix and Scottsdale – major convention destinations.

For Tucson and Flagstaff, legal options are limited. Municipalities or counties adversely affected by state legislation such as Arizona's can sue for a “declaratory judgment,” says Joel Jacobsen, an assistant attorney general in New Mexico.

But those judgments, if granted, don't really have teeth, says Mr. Jacobsen. A declaratory judgment "doesn't involve the transfer of money between the parties."

Cases where cities have sued their states are rare, says Ira Mehlman, spokesman for the Federation for American Immigration Reform (FAIR). Citing research from FAIR's legal department, he says cities theoretically have the right to challenge policies imposed by their states, but it's complicated.

“Under our system, cities derive their powers from the states in which they are situated. Thus, cities are compelled to comply with state laws unless those laws violate the US or state constitution," says Mehlman. "That is clearly not the case here. [The Arizona immigration law] merely requires police in Arizona to enforce constitutional immigration laws when they reasonably suspect those laws are being violated,” he adds.